


The Dying of the Light

by dragonashes



Series: Quintessence: Undertale One-shots [14]
Category: Undertale (Video Game)
Genre: Determination (Undertale), Gen, Implied/Referenced Character Death, Spoilers - Undertale Genocide Route, Spoilers - Undertale Pacifist Route
Language: English
Status: Completed
Published: 2017-01-19
Updated: 2017-01-19
Packaged: 2018-09-18 13:13:05
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 1
Words: 3,620
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9386789
Author URL: https://archiveofourown.org/users/dragonashes/pseuds/dragonashes
Summary: Undyne the Undying succeeds...then must come to terms with what she has become.





	

**Author's Note:**

> Inspired by “Do not go gentle into that good night” by Dylan Thomas, which begins:  
> “Do not go gentle into that good night,  
> Old age should burn and rage at close of day;  
> Rage, rage against the dying of the light.”  
> [Text is under copyright, but has been made available for viewing here.](https://www.poets.org/poetsorg/poem/do-not-go-gentle-good-night)

Her roar echoed over the battlefield.  Before her, on rocks worn smooth by generations of monsters, lay the broken body of the human.  No - whatever it was.  The  _ demon _ that wanted to destroy everyone.

A part of her tensed, but she didn’t know why.  It seemed...almost too good to be true.  She’d been told that humans didn’t turn to dust when they died, but seeing it in person was surreal.  She half-expected it to get back up and keep on swinging.  The  _ thing _ had been so persistent, so  _ determined _ that it was hard to believe that it was...over.

Breathing heavily, Undyne examined herself.  She felt surprisingly good, all things considered.  The front of her armor, where she still felt the lingering pain of the human’s strike, was now whole.  It hadn’t been mended; it had been...transformed.  Her breastplate and gauntlets now bore soul-shaped marks; her shoes and epaulettes were spiked.  It was...strange.

She raised one hand to her left eye, the one that had been torn out in a fight so many years before.  The eyepatch she’d worn over the empty socket was gone, and she could feel...something coming out of it.  Some kind of magic.  It didn’t feel...right, really, but…

This.

Was.

AWESOME!!!

Just wait until she showed Papyrus!!!

That thought brought her up short.  Papyrus, she remembered, was...gone.  Most of Snowdin was gone.  Half of  _ Waterfall _ was gone.  At least the highly-populated areas around Hotland and the Core were safe, but...so many good monsters had lost their lives to this...this  _ demon _ .

At least Alphys had managed to evacuate some of the civilians.  Waterfall was better off, having more advance warning; they would mourn, then eventually go on.  Snowdin would still be around, though their population had been decimated.  They would need new sentries; all of them had fallen in defense of their town.

Well...not _all_ of them, she remembered.  Sans was still out there, somewhere.  He was the _senior_ _sentry_ in Snowdin, now.

What a thought.

She made a mental note to check on him, soon.  After she dealt with...whatever was going on with her body.  Papyrus was - had been -  _ everything _ to him.  If Undyne felt Papyrus’s death like a missing limb, how would Sans react?

Argh!  This wasn’t the time to be all mopey!  Undyne forced herself to focus on the demon lying in front of her.  It’s soul was still present, though crumbling.  Pah.  She carefully reached for it -

“Don’t.”

Undyne jerked against the boney hand that had closed around her arm, surprised when she nearly knocked Sans off his feet with the movement.  He’d always been a puny little one-HP monster, but he usually put up more of a fight…

“Wait, what do you  _ mean _ ‘don’t?’  The soul needs to get to the king!  This is the last one - we’ll be free!  We can finally get revenge on them for everything they did to us!”

“Look at yourself.  You can’t carry a human soul like... _ that. _ ”

Undyne looked.  Sure, she was looking a little...drippy...but what did that have to do with a soul?  “Whatever, punk!  Just let me-”

“ N o . ”  He looked...weirdly serious.  “Look.  You need to go see Alphys.  Now.  I’ll take the soul to the king.”

“What?  I can’t just…”  She coughed, and it was...wet.  It felt awful.  “What can  _ Alphys _ …”  She coughed again, despite her best efforts.

“Right.  Off we go.”  Sans turned the soul blue with one hand, wrapped the other around one of Undyne’s biceps, and started walking.  She followed.  She wasn’t so proud that she couldn’t recognize when she need help.  The walk through Hotland was gonna be rough, though.

“Heya, Alphys.”

“S-sans?   _ Undyne? _ ”  Alphys’s eyes were huge behind her glasses as she took in Undyne’s appearance.  Undyne wasn’t sure why she was so surprised; the cameras were on, still focused on the human’s body-

“Wait.  How’d we get to the  _ lab? _  You’d better have a good explanation for this, Sans…”

“Sorry, got a soul to deliver.”  Sans shoved his hand in his pocket and disappeared around a corner.  By the time Undyne went to look for him, he was...gone?

...That explained how he worked so many jobs at the same time, at least.

“H-he does that sometimes,” Alphys said.  She was twiddling her thumbs, not quite meeting Undyne’s eyes.  “We should r-really take a look at that’s going on.  I mean.  Um.  If you don’t mind.  That looks...worrying.”

“You can say  _ that _ again.  I looked SUPER COOL during that fight with the human, but...I don’t think I’m supposed to be, uh, dripping.”

“O-o-oh dear!”  Alphys ushered the captain through a door Undyne didn’t recognize.  Inside was a small examination room: a low bed, table, chair, and some kind of fancy doctor gizmo.  “Here, let me see your soul.”

It was weird, seeing Alphys so focussed.  Normally the little lizard talked about anime and human history, raving on about giant swords and warrior robot princesses.  Undyne felt a little disappointed; it was the doctor’s passion that she admired so much.

This Alphys looked...lost.  Hopeless.  Undyne wanted to scream at her.

“P-please, stay still!  I need to stabilize you!”

Undyne huffed, but did as she was told.   _ Party pooper. _

“Heya, guys,” Sans said, walking into the room like he’d just been around the corner the whole time.  “What do we need, Alph?”

“I-I think we need the e-extractor.  I’m trying to stabilize her, but…”

“BUT WHAT?”  Undyne yelled.  “CUT THE SCIENCE CRAP AND TELL ME WHAT’S GOING ON!!”

To her surprise, Alphys wouldn’t meet her eyes.  She stuttered something about an elevator and scrambled out of the room.

“You’re falling,” Sans said, his eye sockets black and empty.  “I know you don’t believe me yet, but...that’s what’s happening.”

“WHAT?  Is that what the goopy stuff is??”  Undyne rubbed her fingers together, slightly intrigued by the slimy texture she could feel.

...Which was especially weird since she was still wearing her gauntlets…

“Stop that!”  Sans made a gesture like he was going to grab her arm, but jerked back at the last second.  “Look.  What do you know about DETERMINATION?”

She thought.  “Uh...I’ve heard Alphys talk about it sometimes, but I don’t pay attention to all that nerdy crap.  Why?”

“What do you know about that funny tea Alphys gives you when you visit?”

“...It tastes weird??  But that doesn’t...what does that have to do with THIS?”  She raised her arms.  Splatters of what was once her armor (probably??) fell to the floor.

“Okay.  Back to the beginning.  So...human souls are different from ours.  They have something called DETERMINATION.  It’s extremely powerful; it’s what makes human souls so strong, actually.  Enough of it in proximity to monster magic can even create an anomaly in the timeline.”

“WHAT THE HECK DOES THAT MEAN??”

“Uh, they can mess with time.”

“WHAT DOES THAT HAVE TO DO WITH MY DRIPPING PROBLEM???”

“I’m gettin’ there, don’t worry.  So...DETERMINATION is strong.  It’s basically concentrated will to live.  The Royal Scientist before Alphys experimented a lot with it, trying to find a way to infuse monsters with DETERMINATION.”

“Why?”

Sans looked at her.  “You know how monsters fall down when they lose hope, or go through a heartbreak, or basically get too sad?  They just...stop working?  Humans don’t do that, not the way we do.  They hold on.  They fight for their own lives.  Sure, some humans might give up on life, but their bodies and souls still keep going.”

“So...what?”

“Ya know the big crisis a few months back, when all those monsters fell down?”

Undyne nodded.  It still hurt to think about all those monsters.  “Alphys is helping them, though.”

Sans closed his eye sockets and sighed deeply.  “Alphys...found the previous Royal Scientist’s notes.  She was able to extract DETERMINATION from the king’s human souls using a machine he left behind.  She thought...she thought that giving fallen monsters DETERMINATION - the will to live - would get them back on their feet.  And it did.”

“WHAT?  That’s AWESOME!!!  I KNEW she could do it!!!  But...then why haven’t they gone home yet?  You know how much Shyren wants to see her sister!  You know how much trouble the dogs are without the older members of their pack!”

“DETERMINATION...it isn’t something to mess around with, Undyne.  It worked, sure; for a little while.  Then they started to…”  He gestured towards Undyne’s dripping arms.  “Well, they aren’t really...fit for company anymore.”

Undyne sat back, startled.  “Wait, so, they’re...dripping?  Like me?  But I don’t have DETERMINATION.  I’ve never fallen down!”  She thought back to Sans’s earlier comment, about the tea.  “Wait.  Wait.  You’re saying...that Alphys has been giving me DETERMINATION????”

“Y-yeah,” came a small voice from the doorway.  Alphys peaked around Sans, keeping him between her and Undyne.

Undyne growled.  “COME AND FACE ME LIKE A REAL MONSTER, PUNK!”

“U-um…”  Alphys dithered, hopping from one foot to the other.  Sans finally stepped out of the way, a hand on her shoulder as he maneuvered her in front of Undyne.

“WHY WOULD YOU DO SOMETHING LIKE THAT!!  ESPECIALLY WITHOUT TELLING ME!!”

“I...I measured the d-dosage carefully.  I knew that w-what happened to those o-other monsters wouldn’t h-happen with the amount I gave you.  I just...w-wanted to give you a-another chance, if something h-happened.”

“Don’t be too hard on her,” Sans piped up.  “It worked, if you remember.  If you didn’t have DETERMINATION, the human would’ve taken you out in one hit.”

“YEAH, RIGHT!  I’M TOUGHER THAN THAT!”  But Undyne  _ did _ remember.  She remembered the power behind the human’s strike, how the hatred had burned right through her defenses like they were nothing.  She remembered how her body had felt like it was splitting apart, like she was falling into nothingness.

She remembered the feeling of  _ strength _ that had surged through her body, REFUSING to let her give up and die.

Sans gave her a knowing look.  “It’s pretty cool, huh?  Feels like you can do anything,  _ be _ anything, and nothing in the world can stop you.”

“YEAH!  If this is how humans feel all the time...I can see why they’re so STRONG!  HAHA!”  Her laughter was cut off by another wet cough.

Alphys grabbed Undyne’s arm.  “O-oh dear.  Hang on.  W-we need to get you down to the extractor.  If we can get the excess DETERMINATION out of your system...m-maybe you’ll be okay.  Sans?  Can you help me?”

Sans was already halfway out the door.  “I think you’ve got it handled, Alph.”

“P-please?”

“I told you, I’m never going back there.   _ Never. _ ”

“ _ Please _ Sans!  I can’t do this alone!  Undyne...Undyne’s going to  _ die _ right in front of me and  _ I can’t save her! _  Not alone!  Please!”

Sans paused, turned to look at Alphys, and sighed.  Undyne wasn’t sure what he read in the little lizard’s face but it seemed to sway him.  He took a long look at Undyne, then turned back around and walked towards the...bathroom?

Alphys helped Undyne back onto her feet and led her in the same direction.  “J-just hold on,” the scientist muttered.  “We’ll fix this.”

The bathroom turned out to be an elevator.  Undyne approved; it was the perfect SECRET DEFENSE!  It felt like they were going straight down to the lava level!  Unfortunately, the other passengers were apparently too caught up in sciencey thoughts to properly appreciate it.  They weren’t even screaming and throwing their hands up.

(...Papyrus would have thrown his hands up and screamed with her.)

She decided that she’d had enough.  “So...what’s the story with you two?  I didn’t realize you knew each other.  You into that science stuff too, Sans?”

The skeleton looked sideways at her.  “I used to work with the previous Royal Scientist.  Alph asked me for some input when she took over.”

Alphys was studying her toes, looking embarrassed.  Weird.

“So...why are you here?  I thought you’d be back in Snowdin, preparing a funeral for-”

“D o n ‘ t .”  Sans’s eye sockets were black again, and his voice was...strange.

“Psh.  Fine, fine.  I’m just surprised you’re here.”

Sans didn’t answer.  Alphys had practically crawled into her corner of the small elevator, trying to be as invisible as possible.

...This is why Undyne hated hanging out with NERDS!  They were so AWKWARD!  And not that good kind of awkward!

Also, what was up with Alphys?

The elevator opened before she could ask.  On the other side was a dark, cavernous...lab?  It looked like Alphys’s lab a bit, and there were science-y words on the walls, but it was hard to tell.

Sans led the way down a hallway, while Alphys lagged behind and supported Undyne.  He seemed to know his way around, so Undyne wasn’t too worried.  She was starting to feel really, really sick, actually.  She mentioned it to Alphys, whose only response was to walk faster.

They walked through a room full of beds, and Undyne was disturbed to see that all of them were empty.  Where were the monsters?  Alphys wouldn’t respond when she asked.  There seemed to be something lurking just out of sight, but it was in Undyne’s blind spot and the two nerds were rushing her through the rooms too fast to get a good look.

Finally, they reached a room with a big hole in the center.  It reminded Undyne of the chasms in Waterfall, all endless and empty.  Then again, it was hard to see around the giant skull-shaped... _ thing _ hanging over the pit.

“It’s the D-DETERMINATION Extractor,” Alphys explained.  “Hopefully if we, um, remove the extra DETERMINATION, you’ll stop...dripping.”

“That’d be GREAT!  Let’s GO!”  Undyne leapt towards the machine, the motion hindered by a lizard scientist who was still dangling off her arm.

“No!  Please!  Wait!  You can’t -  _ urgh! _ \- you’ll break it!  We have to do calculations first!  Math!  We need Math!”

“WELL THEN, HURRY UP AND MATH!”  She was really feeling...pretty sick.

Undyne didn’t know how long it took Alphys and Sans to mutter and scribble on their notepads before they let her anywhere near the machine.  It didn’t  _ matter _ how long it took.  What  _ mattered _ was that she was starting to lose feeling in her fingers and toes, and it was making her very, very worried.

Undyne was a warrior.  It was all she’d  _ ever _ been.  For as long as she could remember, she had fought, trained, clawed her way up the ranks.  She’d gone from a no-name urchin in Waterfall to King Asgore’s student on her own merit alone.  She’d been accepted into the Royal Guard using the king’s training, but none of his influence.  It had taken a lot of time and hard work, but she’d soon become the youngest Captain the Guard had ever seen.

If Alphys and Sans couldn’t put her back together...what would that mean?  Would she still be able to fight?  She had faith in Alphys - she really did - but...Sans’s comments about the missing monsters were worrying.

At Sans’s direction, Undyne climbed over the chasm to the skull-shaped thing.  She teased him for using his blue magic on her, but deep down she was grateful for the backup.  That hole looked...really, really deep…

“A-are you okay?”  Alphys asked, once Undyne was settled.

Undyne gave her a double thumbs-up.  “Let’s get this sciencey thing STARTED, NERDS!”

“Okay.”

A whirring filled Undyne’s ears.  She could see Alphys’s mouth moving, and Sans gesturing like he was responding, but she couldn’t hear a thing over the noise.  It kept...getting  _ louder _ .  It stopped just short of painful, but the level of noise was SO IRRITATING!  It made her want to PUNCH something!

Then Alphys flipped a switch, and Undyne’s world went  _ mad. _

Colors and shapes flashed before her eye in a kaleidoscope pattern.  It was impossible to focus - impossible  _ not _ to focus - impossible to feel or hear or think or

_ WHAT _

_ IS _

_ GOING _

_ ON??? _

There was a tugging on her soul, familiar and completely unfamiliar at the same time.  It felt a little like Papyrus’s blue magic, when he’d drag her down and make her jump over his special attacks, but...not quite.  It was almost as if something was draining out of her.

That...that was good, right?  That’s what was supposed to happen, right?  She started feeling shaky; not from fear, but from...weakness??  Why was she feeling SO WEAK??  She tried to get Alphys’s attention, but it was impossible to hear over the roaring of the machine.

Then, everything stopped.

Ears ringing, Undyne sat up.  It took her more effort than she wanted to admit, but she made it.  Sans was there at the edge of the pit, hand raised to catch her with blue magic if she fell in or something stupid like that.

“So...did it work?”  She asked.

Sans’s expression was unreadable.  “Let’s get you over here and we’ll see, huh.”

Once on solid ground, Undyne collapsed.  She was starting to feel numb.  Something had gone wrong, right??  This wasn’t  _ normal, _ right??

“Undyne, d-do you mind if I ch-check your soul?”  Alphys asked, another one of her strange doctory devices in one hand.

“Uh, sure, go for it.”

Alphys’s eyes went wide when she saw the results.  “S-Sans!  This is…”

The skeleton looked over her shoulder.  “Oh.  Huh.  That’s...not good.”

“WHAT!”  Undyne yelled.  Her voice was hoarse and her throat  _ hurt _ .  “WHAT IS GOING ON!  WHY DO I FEEL LIKE A WIMPY SPAGHETTI NOODLE!”

“You need to see this,” Sans said, handing the device to Undyne.  It must be bad, then, if he missed the opportunity to make a pun-

Oh.

_*UNDYNE THE UNDYING_  
_*99 ATK_  
_*1 DEF_  
_*3 HP..._

“WHAT THE HECK!?!  HOW DO I ONLY HAVE THREE HP??”

“Hey, don’t knock us low-HP types,” Sans said, giving her a lazy grin.  “It’s not so bad once you get used to it.”

“ARGH!  I’M NOT A - A LAZY SENTRY WHO SLEEPS ALL DAY!  I’M THE CAPTAIN OF THE ROYAL GUARD!!  HOW AM I GONNA LIVE LIKE THIS???”

“At least you’re stable now,” Sans said.  “You could  _ actually _ be dead right now, y’know.  Alphys did a great job on the calculations; you should thank her.”

Undyne turned to the Royal Scientist, who was cowering in the corner.  “I...uh...thanks, Alphys.  I...I really owe ya one.”

“B-but you’re...you’re…”

“Hey.”  She slowly shuffled over and laid a hand on Alphys’s shoulder, very glad that she wasn’t gloopy anymore.  “You did your best, right?  OWN IT!  Be PROUD!  You saved my life!  And yeah, I’m not...happy...about my HP situation, but I’ll live!  If  _ that _ lazy butt-”

“Hey,” protested Sans, not actually sounding very offended.

“-can make things work for him, I can to!  I have THREE TIMES the HP he has!  HA!”

“O-okay,” Alphys said, taking a deep breath.  “W-well, I need to feed the amalgamates.  Um.  The other monsters, I mean.  You c-can rest here if you want.  I’ll be back...soon.”  She fled.

Sans immediately slouched to the ground by the wall and closed his eyes.  After a moment’s hesitation, Undyne joined him.  She tugged her gloves off, relieved when they actually came off.  She tried not to think about the stickiness that coated the insides.

Three HP.   _ Three HP. _  How was she going to be the Captain of the Guard now??  Everyone knew Asgore was a big fluffy pushover; he couldn’t bear to see anyone get hurt.  He’d have her off the guard in an instant rather than risk her life.

What was she gonna do  _ then? _

“You could always help me with my hot dog stands,” Sans said.  He really was way too good at reading faces.  “If, you know, you want something to do.  Plus, you can’t attack shopkeepers.  It’d keep you out of trouble.”

“Sit around all day and watch monsters STUFF THEIR FACES??  I don’t think so, punk!  Besides, Asgore has the last soul!  We’re gonna take this war to the humans now, right??”

“Maybe.  Soon.  Asgore seemed...reluctant when I gave him the last soul.  He said he had a lot of thinking to do.  You have some time before things start getting hectic.”

“Not a lot.  Everyone knows there was a human; it was all over the news.  Heck, we evacuated everyone from Waterfall to Hotland and half the Capital.  People are gonna want to see the surface real soon.”

Sans hummed.  “There were a lot...a lot of good monsters who fell today.  Folks will need some time to clean up.  Get their lives together.  They’re not gonna want to jump right into a war.”

“Hey…”  Undyne put a hand on Sans’s shoulder, pausing when he stiffened noticeably.  “I...I’m sorry about Papyrus.  I...he was a good…”  A good many things, really.  A good sentry.  A good trainee.  A good sparring partner.  “A good...friend.”

“Yeah.”

“Do you want to talk about-”

“No.”

“Okay.”  They sat in silence for a bit.  “So...I know I’m not family, but...do you mind if I help?  With Pap’s funeral, I mean.”

Sans sat still and tense for a long moment.  Then, slowly, he turned to face her.  “I think...I think he’d like that.  You were his best friend, y’know.”

“Yeah.”  And it was a real shame, that so many monsters overlooked such a kind and caring soul.  “We’ll give him a good sendoff.”

And then they would break the barrier and Undyne would  _ annihilate _ the humans that did this to him, regardless of her HP.  She would  _ never _ lose another friend to a human.

Humans would  _ fear _ the name of Undyne the Undying.

(...It was a  _ really cool _ name, though!!!)

**Author's Note:**

> An additional debt of inspiration goes to:  
> SharaX for an awesome rendition of ["Battle Against a True Hero,"](https://www.youtube.com/watch?v=DurGJTiMJD8) which is one of my favorite Undertale songs.  
> Tratser, author of the serial comic ["The Thought,"](https://tratserenoyreve.tumblr.com/mycomics) featuring an Asgore reluctant to actually act after obtaining all seven souls (and a Sans with nothing to lose...).  
> blinkpen, author of the much shorter comic ["Undyne the Unkillable,"](http://blinkpen.deviantart.com/art/Undyne-the-Unkillable-567034944) which includes a goopy and DETERMINED Undyne.  
> Zarla-s, author of the Handplates comics, for fun theories on Undyne's friendship with Papyrus. [This one](http://zarla.deviantart.com/art/Put-em-all-in-a-basket-617911469) is especially applicable; Sans doesn't trust Papyrus to just anyone, after all.
> 
> Thanks for reading! I hope you enjoyed. I've seen several works about a genocide run that ends at Sans (and it's heartbreaking), but none that end at Undyne. We know that Undyne gets some unidentified tea from Alphys, and many folks hypothesize that she has just enough DETERMINATION for a second try...but we know it's dangerous. I got to thinking: Undyne's pretty messed up by the time you fight her the second time. If you fight her on a neutral run, she...basically melts. It's nightmare-inducing. But what if she COULD survive?
> 
> If you want to see more, please follow my author profile or the series, "Quintessence: Undertale One-shots." I post most Wednesdays and Saturdays, barring power outages, family emergencies, or AO3 weirdness. I have some longer stories I'm wrapping up; those will be posted when complete.


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